How air affects human comfort in a building

displacement diffusers - 1
People spend approx. 90% of their time indoors, i.e. in an artificially created climate. Therefore, buildings and their technical equipment should be designed and erected so that to ensure favourable thermal conditions for their inhabitants.
Author
Monika Garbacz

Technical sales advisor – SMAY

Certainly, each of us has sometimes felt certain discomfort due to draughts or too high temperature in rooms. So it can be assumed that we suffered from thermal discomfort at the time. How do you ensure thermal comfort then?

Thermal comfort is a state in which a human feels ideal microclimatic conditions. Wellbeing is a result of the human body’s thermal balance versus the environment, i.e. when we feel neither cold nor hot. Thermal comfort is a subtle combination of physical (i.e. temperature, humidity, airflow rate) and mental factors. Adaptation to the existing microclimatic conditions depends on our metabolic rate and individual preferences. Everyone has their individual requirements concerning climate and therefore it is impossible to satisfy all the people staying in the room. However, experts managed to establish the general rules of designing buildings that prove comfortable at least for most users.

Building air quality testing – a response to the needs of users

Temperature and air flow speed in a zone occupied by people have a significant impact on their feeling of thermal comfort. We feel thermal discomfort when the level of activity is quite low, while the stream of supply air causes draught, and with a relatively small amount of generated energy there comes a rapid heat loss. In fact, a properly designed, built and adjusted ventilation system remains completely unnoticeable to the user. The proper indoor air distribution has a significant influence on the comfort of building users. Thus, it is crucial to choose the right diffusers which are the most important component shaping the air distribution. A wide selection of products offered by SMAY enables designers to select the right solutions and create a ventilation system for each room type.

Air exchange in the office and sick building syndrome

The most significant advantage of using diffusers is the possibility to supply a large amount of air at a temperature lower than the room temperature, without causing any discomfort to people. To counteract the phenomenon of warm air being entrapped in the upper section of the room, the ALDA and SDA diffusers are available with air blades which allow 1-, 2-, 3- or even 4-way air supply. Whereas the NZD rectangular diffusers, with blades of 360° move range which can be adjusted to individual users’ preferences, allow the designers to shape the supply air stream in any selected manner.

The high degree of air stream induction is ensured by the NSAL slot diffusers which properly direct the airflow via a system of separately adjusted blades. The NSL diffusers can be equipped with 1 up to 4 slots with fixed, modular blades which allow vertical, horizontal or diagonal air supply, with the option of alternate positioning of the blades in a single slot.

For the purpose of air supply in rooms which require high thermal comfort, we offer the NSAL-70 and NSAL-72 air handling units for fixed or variable capacity. A unique feature of the air handling unit is its faceplate design which allows for the maximum use of the Coandă effect. A specially profiled air intake surface maintains a constant level of sound power generated by the unit.

displacement diffusers

The most significant advantage of using diffusers is the possibility to supply a large amount of air at a temperature lower than the room temperature, without causing any discomfort to people. To counteract the phenomenon of warm air being entrapped in the upper section of the room, the ALDA and SDA diffusers are available with air blades which allow 1-, 2-, 3- or even 4-way air supply. Whereas the NZD rectangular diffusers, with blades of 360° move range which can be adjusted to individual users’ preferences, allow the designers to shape the supply air stream in any selected manner.

The high degree of air stream induction is ensured by the NSAL slot diffusers which properly direct the airflow via a system of separately adjusted blades. The NSL diffusers can be equipped with 1 up to 4 slots with fixed, modular blades which allow vertical, horizontal or diagonal air supply, with the option of alternate positioning of the blades in a single slot.

For the purpose of air supply in rooms which require high thermal comfort, we offer the NSAL-70 and NSAL-72 air handling units for fixed or variable capacity. A unique feature of the air handling unit is its faceplate design which allows for the maximum use of the Coandă effect. A specially profiled air intake surface maintains a constant level of sound power generated by the unit.

A characteristic feature of swirl diffusers is the very swirl of the air stream delivered into the room, which mixes the air within the room with the supplied air. Depending on the position of the blades, the air stream can be directed along the ceiling or immediately towards the occupied zone. Our offer includes a wide range of swirl diffusers. For instance, the NWC swirl diffusers of variable geometry are particularly recommended for rooms where an important parameter is the precise setting of the end speed of air supplied to the occupied zone. The speed is adjusted by separately setting each of the 4 integrated blade units. Some of the most popular diffusers are the NS-8 with movable blades which allow the user to freely shape the airflow as well as to have the supply airflow swirled.

The NSCT units belong to the category of displacement diffusers designed to distribute air directly to the occupied zone. The centrifugal air distribution method allows for increased induction and rapid equalization of air temperatures in the occupied zone. The air from the diffuser heats up spontaneously once it has encountered a heat source. The result is the so-called thermal chimney that lifts heated air and volatile pollution particles towards the ceiling. Then, the pollutants are removed via a separate exhaust system.
When designing a ventilation system, one should remember that every single detail is decisive for both human comfort inside the building and the costs of operation. The air diffusers correctly selected to the operating parameters, proper for the type of a room, its size and the height of the occupied zone, are important components of any ventilation system which shape the air flow pattern as well as the thermal and acoustic comfort in the room. The speed and temperature of supply air should be adjusted so not to cause a feeling of cold, excessive heat or draught.

Safety Way: an innovative differential pressure system – escape routes free from smoke and fire – highest degree of protection.
The Safety Way differential pressure system is a solution designed for multi-storey buildings:

• iSWAY-FC® differential pressure product for smoke and heat control systems;
• Innovative predictive algorithm;
• Anti-Frost system that endures even the most extreme weather conditions;
• 24-hour automatic test of all the components;
• Automatic adaptation to changing service conditions;
• Communication between individual components of the set and continuous tracking of all components (regulators, remote pressure sensors, etc.);
• Continuous measurement of the set value of static differential pressure between the protected and reference zones by the P-MAC(F) sensor.

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